As described in the Adams et al application referred to above, the sharply increased cost of locomotive fuel in the past several years has caused increased efforts in the railroad industry to reduce tare weight of rolling stock, since fuel consumption is related to the gross weight of the shipment (train plus cargo). While reduced weight is an important consideration in any type of shipment, it is especially important in piggyback (highway trailer or container carried on a flatcar, hereinafter TOFC and COFC, respectively) shipments, where the tare weight of the trailer or container is in addition to the tare weight of the flatcar. This "double tare" weight handicaps the rail mode of transportation in its competitive position vis-a-vis highway transportation for containerized cargo, even though the latter is generally considered to be less efficient in its use of fuel.
Piggyback traffic is generally carried on flatcars of 85 to 89 feet, 4 inches in length. These cars can readily handle two trailers or containers 40 feet long or less; however, in recent years, the 45-foot highway trailer has come into popular use and presently constitutes a large percentage of the total production of highway trailers. Two 45-foot trailers cannot be carried on an 89-foot flatcar, and so it often happens that only one 45-foot trailer is carried on an 89-foot car, thereby further reducing the fuel efficiency of the operation.
The construction of longer cars to accommodate two 45-foot trailers or containers to remedy this problem is impossible because the railroad industry through its industry association, the Association of American Railroads (AAR), has placed a length limit of 89 feet, 4 inches on any cars constructed in the future. This length restriction is necessary because of operating problems inherent in long cars having long end overhang (beyond the railway trucks). Typically, the cars tend to pull off curves in conditions of heavy pull and to jack-knife under heavy buff forces. Additionally, the geometry of long cars causes them to track poorly, and with the long end overhang there is a tendency for the air hose connections between cars to separate in operation and cause an emergency application of the train air brakes. Still further, long cars must be made quite heavy in order to support the carried weight which is concentrated at the center of the car where the adjacent ends of the two containers or trailers are supported, thereby adding further construction expense and burdens to the pulling equipment. The arrangements described and claimed in the aforesaid Adams et al application go far in overcoming bulk cargo transportation problems of the kind referred to above. However, ordinary car braking arrangements of the kinds heretofore known in the prior art still leave much to be desired as regard safe and effective braking means for the articulately interconnected cars of the kind described in the aforesaid Adams et al application--and especially with increasing numbers of cars and therefore longer trains.
Accordingly, one object of the present invention is to improve the efficiency and safety of the braking means for such piggyback equipment by providing a unique multiple track handbrake arrangement for a railway car assembly for transporting a number of trailers or containers.
Another object of the invention is to provide an effective handbrake means for a railway car assembly of the piggyback variety for carrying variously sized trailers or containers.
Another object of the invention is to provide a railway car assembly of the piggyback variety having improved handbrake operating characteristics.
Still further and other objects of the invention will become apparent as the description proceeds.